Insulin, Adrenocorticotrophic hormone (ACTH), somatostatin, and other vertebrate peptide hormones have been demonstrated in unicellular organisms e.g. E. coli, and higher plants e.g. spinach. Using protein purification techniques including high performance liquid chromatography (HPLC) and affinity chromatography molecules similar to ACTH have been purified to homogeneity. The sequence of these molecules suggest that it may be part of the C-terminal 33 amino acids of elongation factor II of E. coli and may represent the evolutionary origins of vertebrate ACTH. Molecular biology techniques will be used to establish this concept. In addition, rat IGF-I cDNAs have been cloned to assist in the screening for insulin-related genes in primitive organisms. They have also been used to study gene expression in hepatic and non-hepatic rat and human tissues.